#shader vertex  
#version 330 core

layout(location = 0) in vec4 position;  // location is the index of attrib
void main() {
   gl_Position = position;
};


#shader fragment
#version 330 core

layout(location = 0) out vec4 color;

uniform vec4 u_color;

void main() {
   color = u_color; // RGBA
};
